1 files changed, 36 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/journey/nfa/dot.rb b/actionpack/lib/action_dispatch/journey/nfa/dot.rb
new file mode 100644
index 0000000000..56e9e3c83d
--- /dev/null
+++ b/actionpack/lib/action_dispatch/journey/nfa/dot.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module ActionDispatch
+  module Journey # :nodoc:
+    module NFA # :nodoc:
+      module Dot # :nodoc:
+        def to_dot
+          edges = transitions.map { |from, sym, to|
+            "  #{from} -> #{to} [label=\"#{sym || 'ε'}\"];"
+          }
+
+          # memo_nodes = memos.values.flatten.map { |n|
+          #   label = n
+          #   if Journey::Route === n
+          #     label = "#{n.verb.source} #{n.path.spec}"
+          #   end
+          #   "  #{n.object_id} [label=\"#{label}\", shape=box];"
+          # }
+          # memo_edges = memos.flat_map { |k, memos|
+          #   (memos || []).map { |v| "  #{k} -> #{v.object_id};" }
+          # }.uniq
+
+          <<-eodot
+digraph nfa {
+  rankdir=LR;
+  node [shape = doublecircle];
+  #{accepting_states.join ' '};
+  node [shape = circle];
+#{edges.join "\n"}
+}
+          eodot
+        end
+      end
+    end
+  end
+end